Pump



B. S. AIKMAN June 7, 1932.

PUMP

Filed July 25, 1928 3 Sheets-Sheet l [/2 yen for L llll I ll/h.

B. S. AIKMAN June 7, 1932.

PUMP

Filed July 25, 1928 5 Sheets-Sheet 2 [/2 z/enfar Barim J. cm

June 7, 1932 B. s. AIKMAN 1,861,732

PUMP

Filed July 23, 1928 3 Sheets-Sheet s Patented June 7, 1932 PATENT FFICEF- BURTON S. AIRMAN, OF MILW AUKEE,".TISCONSIN, ASSIGNOB TO'NA'DIONAL'BRAKE-GE- ELECTRIC COMPANY:, OF IYIILWAUKEE, WISCONSIN, A- CORPORATION- OF WISCONSIN PUMP Application filed July 23,

My invention'relates to pneumatic pumps and more particularly to a method of and means for preventing frosting. or freezing; of the exhaust valve or'adj acentparts While the pump lS:'lI1 operation.

Pneumatic pumps of the type disclosed in my priorfPatent1,658g032'0ft February 7th,

1928; arenow employed in. car \vashing'systemsand the'like,zthat is, systems Where air and water under high pressure are projected through a suitable nozzle for Washing auto mobiles, etc. The air pressure employed is ofthe order of-lOO to 150 lbs. gaugepressure, that is approximately 7 to 10 atmospheres.

This pressure prevails-in both the nozzle and:

in the air pumping chamber andis required in order to get the necessary atomizingand scouring; effect; The pump chamber may exhaust into atmosphere or into'th'e intake of the 'compressor but at all events: the pressure drop is very considerable. Under the Wellknown ISlZttlOIIbGt-WGGII pressure volume and temperature as set out in'the lawsof Charles and of Boyle, pressureavolumeand temperature are interrelated: variables. This relation-is familiarly expressed'in the equation PV equals KT. here P is pressure V is volume, and T is absolute'temperature and K. is asultable constant.

Hence a drop inipressureis accompaniedby anmcrease in volume and; unless special provision is made to prevent thesame, by a drop in temperature. i

The point Where the high'pressure'inthe pumping. chamber is released isthe exhaust valve and its cooperating port. The rapid expansion of the air tends to-lower the temperature of the exhaust valve,- and where, as in' car washing; the pump iscalled on tooperate continuously forhours at a time ata high rate of water delivery, the exhaust valveand its surrounding valve seat become so chilled as to form frost or ice whichfinallyinterferes With-the operationof the valve.

I have studied the difficulty andendeavored to find means for preventing interference with the exhaust valve by frosting. Any

means for applying-heat from'usual heating? meansrsuch as gas,- electricityg steam or the like,.or the employment ofhote air would add 1928. Serial No. 294,912.

unbearable complications besides addin'gf'a' possible danger to the operator and to th'e mechanism. Furthermore agreat deal of heat W-ouldbe required for continuous operation.

I have observed that water contains arelatively great amount of latent heat. Even if wateris at freezing temperature, it Will not freeze until it loses its latent heat of fusion.

This means that the formationoffrost ca'nbe prevented by a bath'of Watereven if the same" is but little above freezing. I have conceived the idea of Washing the exhaust valve'with some of the Water employed in the pump chamber to prevent frosting or freezing.

stroke of tlie pump: Preferably. this squirt occurs during the outrush ofa'ir'orduring the I latter part ofthe exhaust so that the squirtof' Water is caused to reach all the desired parts and to be carried out of the Way of the exhaust valve and its port;

In this manner the bathing of the exhaust valve isgraduated in accordance with the amount-ofair exhaustedtherethrough so that frosting is eliminated.

In the preferred form of the inventionthe I Water for bathing the exhaust valve is taken from the discharge connection, thatis, on the remote side of the water discharge check valve, through the clearance of the discharge check valve stem so as to remove'a'ny'san'd or other impurities Whichmight tend'to become lodged in the clearance space about thestem. In many cases in pneumatic pumps sand" orother impurities are carried With-the Water, particularly during the initial installation.

and this may become lodged either in the clearance space or beyond the stem of the discharge check valve. Such lodgment is avoided by the use of the present invention.

\Vhile I shall describe in connection with the accompanying drawings the specific form in which I prefer to embody my invention, it is to be understood that the invention is not to be limited to the specific means which I have herein shown and described, and that in fact widely different means may be employed in the practice of the broader aspects of my invention.

In the drawings,

Fig. 1 is a side elevation considerably shortened with the lower part of the barrel and connected parts shown in section.

Fig. 2 is a vertical section through the head and the upper part of the pumping chamber.

Fig. 3 is a vertical section through the lower part of the pumping chamber, Figs. 2 and 3 when put in vertical alinement constituting a vertical section through the pump; and

Fig. 4 is a section through the discharge check valve box taken on the axis of the discharge check valve stem.

The pump in which I have shown my invention as embodied is of the type originally disclosed and claimed in my prior Patents No. 1,658,031 and 1,658,032, both granted February 7th, 1928, to which reference is here made for a full disclosure of the construction and mode of operation of the parts.

The pump herein shown comprises the head member 1 mounted on top of a barrel 2 providing a chamber 3, which is known as the pumping chamber. The barrel 2 is closed by a foot member 4, which contains the intake connection for liquid to be pumped. The head and foot members are tied together by a tension connection, which includes the discharge pipe 5 threaded into a socket in the lower part ofthe head member 1, a valve box 6 into the upper end of which the discharge pipe 5 is threaded, and a stud 7 which passes through the foot member 4 and 1s held by a cap nut 8 threaded upon the free end of the stud 7.

The foot member 4 has pipe sockets 99 opening into a chamber 11. Water is conducted from the city mains through pipes threaded into either one or both of the sockets 99 where the pump is employed in car washing or like service. The flanges 1212 are formed on rearwardly extending arms 12 formed integral with the foot member 4 and projecting beyond the barrel 2. The flanges 12-12 are formed at right angles to the arms 12 so as to allow the pump to be mounted on a wall or other like foundation and with the barrel in spaced relation therewith, and they are preferably extended in parallelism with the inlets 9.

The inlet chamber 11 opens through an annular valve port 13, suitable webs being provided to bridge the annular valve port 13. The foot member provides a double bead valve seat 14 for the inlet check valve 15 which preferably is an annular disk verticalcylindrical guide member 17 is slotted to lighten the same and to prevent the deposit of sand and the like, and it has three spring seats 19 disposed about its periphery containing inlet check valve springs 20 tending to hold the check valve 15 upon its seat. Thesprings may be omitted where only submergence pressure is depended upon to fill the pumping chamber.

The stud 7 which is threaded into a socket in the lower end of the discharge check valve box 6, has a lock nut 22 for locking the stud in place. The upper end of the stud is recessed axially as by drilling, as indicated at 23, see Figs. 3 and 4, and this recess receives the lower end of a small tube or pipe 24 which extends down from the head member 1 through the water discharge pipe 5 and valve box 6, making a tight connection with the recess 23 by means of a packing ring 25,

which is compressed between the wall of the socket in which the stud 7 is threaded and the end of the stud 7 about the tube 25. The upper end of the stud has an outer peripheral groove 26 which communicates through a drill hole 27 with the recess 23. The groove 26 in turn communicates with a horizontal passageway 28, preferably formed by drilling and plugging the casting of the valve box 6, and the horizontal passageway 26 in turn communicates with a vertical passageway 29 i also preferably formed by drilling the casting.

A nipple 30 providing a raised annular valve seat 31 at its upper end is forced through a counterbore in the upper end of the drilled passageway 29. The valve seat 31 defines a valve port which is controlled by the low level controlled valve 32 having the yield ing face 33 disposed in a recess in the outer arm of a lever 34. The lever 34 is pivoted intermediate its ends on a pin 35, which pin in turn is supported on a bracket member 36 providing two upturned ears or lugs in which the outer ends of the pin rests. The yielding valve face 33 is held in a recess in the arm 37 by means of the screw plug 38 so that the same may be renewed if desired. A wire spring of the hair pin type, indicated at 39 in Fig. 1, has its ends connected as by screw 40 to the valve box 6 and by a screw 41 to the arm 42 of lever 34 respectively. The arm 42 of the lever 34 is Y-shaped reaching around the discharge pipe 5 and having an upturned end 43 adapted to be engaged by the traveling float 44 when the liquid in the pumping 4 with the chamber a,

float 44. presses upon the end 43 of the lever 34; the valve is opened and the internal pressure in the chamber 3 causes liquid to beforced down through the valve passageway 29, lateral'passageway 28,.through drill hole 27, into recess 23' and thence on up through the tube 24 into a motor chamber 45 in thehead member 1 for shifting the air control valve, as will be described later.

The valvebox 6 has a removable valve seat member or plate-47, the'flange of which is bolted to the box 6. An inwardly extending bead or valve seat 48'is adapted to be engaged by the discharge check valve 49, which comprises a metal back 50 and a yielding face 51 mounted upon a stem 52.

The valve member 49 is held ona reduced partofthe stem, as by means of the nut 53. The forward end of the stem providesa guid ingextension 54 mounted ina guide 55 sup ported by spiderarms 56. The rear endof the stem is guided in hub or boss 57; which isdrilled to provide a slight clearance between the stem 52and the bore of the boss 57. The boss 57 has an extension at 58 containing a threaded socket 59 for receiving the threaded end of the. elbow 60. A removable orifice nipple 61 is seated in the end of the elbow where it threads into the socket59 to control the rateof water discharge throughthe clearance space about the stem 57, as will be described later.

The upper arm of the elbow 60 is threads ed to receive a threaded studforming a part of the check valve housing 62; said check valve housing containing a ball check valve 63 seating upon a seat 64 in thelower part of the housing to prevent inward flow of liquid towards the valve box 6 but permitting. outward flow therefrom. The pin 66 prevents the ball check valve 63 from seating. over the end of the tube 67,.which is held to the housing 62 by a threaded union 68. The tube 67 extends upwardly being carried up to the head member 1 and having its upper endsupported by a suitable sheet metal clamp 69, and the end of the tube directed into the lower end of the exhaust passageway 70. Tube 67 is however, smaller than the passage way 70 so. that the latter is in communication as well as with the tube 67.

he head member 1 comprises a head casting 72 having a flanged base 73 whichcooperates with the upper end of the sleeve or barrel 2 defining the chamber 3, and this head casting is suitably cored and machined to provide the passageways and to be fitted-with the various parts hereinafter described The head casting 72 has a transverse passageway sultably' dividedinto various chambers and:

The spring 39 tends at all times to passage-ways;.. andi is. provided? with certain pipe sockets for the attachment of "air admission'and :exhausttpipesan'd a water discharge pipe;

The" exhaust connection is. shown. as a threaded pipes socket: 74;. the air inleticon nection; isr'shown M3175 and the waterdis charge:- connetction: is; not: shownyalthough it will. be understood: that: the same communic-ates with the cored. passageway 76', which. communicates-with: tlie upper: end of the water? discharge? pipe 5;.

The a-ir'inlet connection lcommunicates by way: of: a". cored passageway shown; in. dotted lines in: Fig: with the admission: valve chamber-77 formingrazpartiof the'main' transverse bore through the; head I castiihg72.v A removable :plate v78: defines one wall of: the 2 air admission valve chamber and provides a guide at. 79 for the=stern 80. The motor. diaphragm+orz piston, which: is in the shape of" a" flexible 'diaphragnn is. shown at 71, and it has its margin. clamped; to. the. rim; of? the" transverse borer-through the headicastihg 7 by-themoton chamber cap 81. The-chamber 45 in the.-cap 81 has two: connections one' connection indicated at the passagewayv '82. to ahorizontal' drilled passageway 83 leading to the central: tube: 24.- The other connection is by way of. a passageway 84. which communicates with a drilled passageway 85. leading: to the: exhaustpassageway; 86.-

The" motor' diaphragm- 71 lies: between the chamber 45' on' one-:sideandthe chamber: 87, on the'other; The-1 chamben 87 hastw-oconnections-one; a small leakage orifice 88' drilled throughtheaplate78 which separatesthe: motor chamber." 87 from the: admission valve chambers'7l7. Tliis orifice 88 permits the leakage of live air from; the chamber"77 into the chamber: 87: The'ot-herrconnection vto the. chamben 87 isa port 89 communicating; by way of a: passageway 90. with. a valve-91a The valvea91 comprisesa ball check valve 92' adapted to seat over-"a port: 93 formed. in the valve seat member 94=boltedto the bote tom of theheadflange-73l The plate 94 has au-integralbraclfet: with a.- pivot pin" 95 for the"- valve": actuating lever: 96; one arm of, which, namelythe shorter. arm, has an oper ating-pin 97 adapted'to lift the ball'92 from its seat- 98 when thefl'o'atdrops and the arm. 98 loses its support. from the' floatr The shortv arm' likewise has a stop" 99pad'apted to engage the plate.:94'2to limit the motion of the pin 97. Thearm 98 embraces the'wa-ter discharge pipe 5Ta1ld has: an; outer end: portion 100,

which is adapted to be engaged'bytheupper' surface of'the float 44 When'water has substantially filled'the pumping chamber on the fillingstroke. A small diameter rod or wire 101 has. an outwardlyextending end 102 reaching over a pin 103 in. the slotted end 5, as shown at 104 in Fig. 3. The purpose of the rod 101 is, as explained in the aforesaid Patent No. 1,658,032, to insure that the ball check valve 92 will be raised from its seat 93 at the end of the discharge stroke so that proper reversal of the valve mechanism may be made. The valve mechanism 105 comprises an exhaust valve 106 housed in a chamber 107 which forms a partbf the main transverse bore in the head 1, such chamber being closed on the outside by a screw plug 108 threaded into the head casting 72. The exhaust valve 106 comprises a metal back with a soft facing 109 adapted to engage the annular bead 110 which forms the seat for the exhaust valve 106.

The inlet valve 111 is adapted to seat upon the valve seat 112 which is formed as a shoulder in the bore of the head member 1. The valve 111 has an integral extending sleeve 113 which bears against the central part of the face of the exhaust valve 106. The inlet valve 111 at its opposite end bears against a shoulder on the stem 80, and a threaded nut 114 on the end of the stem 80 holds the exhaust and inlet valves in spaced relation to each other and solidly upon the stem 80. The inlet valve 111 has a loose sliding fit in the cylindrical guide 115 restricting the air flow sufficiently to provide a tendency for the admission valve to snap onto its seat.

The stem 80 is connected to the motor diaphragm 71 by a pair of clamping plates 116 and 117, which in turn are threaded upon the end of the stem 80 to secure these parts together. Movement of the diaphragm 71 is, therefore, transmitted through the stem 80 to the air valve structure including the admission valve 111 and the exhaust valve 106.

The operation of the pump in service will now be described. Assuming that the parts are in the condition and position shown and that live air is connected at the connection 7 5, that exhaust connection 74 is opento atmosphere, that the discharge connection not shown is connected to the delivery passageway 7 6 and that connection to the'city water mains is made at the pipe sockets 99 for supplying water to the pump :as the exhaust valve is open and the admission valve closed,-

live air does not reach the pumping chamber in any appreciable quantlty. However, live air from the chamber77 passes through the orifice 88 into the motor chamber 87 from' whence it escapes through the port 89, passageway 90 and past the valve 92 into the pumping chamber 3.

However, since the exhaust valve 106 is open, such air as escapes during the filling period passes out the exhaust connection. Water enters through the inlet chamber 11, opens the inlet check valve 15 and fills the chamber. As the float 44 is lifted, it permits the low level control valve 33 to seat and close off the connection to the small central tube 24. This puts the motor chamber 45 in communication solely with exhaust through the passageway 85, and the diaphragm 71 is therefore subjected to substantially atmospheric pressure on both sides. The pressure of live air against the admission valve 111 very definitely holds the valves in the position shown in Fig. 2. As soon as the float 44 rises and lifts the arm 98 of the high level control lever 96, the check valve 92 seats upon its seat 93 and prevents the air which leaks through the orifice 88 from escaping into the pumping chamber and out the exhaust. The result is that the pressure flashes up in the motor chamber 45 to a value where the pressure of the same upon a relatively large area of the diaphragm 71 snaps the admission valve 111 ofl its seat and the exhaust valve 106 upon its seat. WVith the opening of the admission valve 111 live air is thereupon admitted through the passageway to the top of the pumping chamber. WVater is then expelled by air pressure, discharging past the discharge check valve 49, discharge pipe 5, chamber 76 and out through a cored passageway in the head member 1, not shown, to the diss charge system which is under pressure. As soon as the float 44 arrives at a position to encounter the projection 43 on the lever 34, valve 33 is opened and water at the pressure of the live air in the pumping chamber is admitted to the central tube 24, passageway 83 and motor chamber 45.

It is true that motor chamber 45 is open to exhaust through the restricted passageway 85, but the restriction of the passageway 85 together with its length prevents the escape of pressure in the motor chamber 45, with the result that the pressures on opposite sides of the diaphragm 71 become sufliciently balanced to permit the pressure on the face of the exhaust valve 106 to snap the valve structure to the right as viewed in Fig. 2.

It is to be observed that as soon as the float 44 has started downwardly on the discharge stroke, the longer arm 98 of the lever 96 provides suflicient weight to press the pin 97 against the check valve 92 to open the same. If, however, this action had not occurred due to excessive pressure on the check valve 92 and insuflicient resistance to water discharge as when the pump is first started, the lever 98 might not be able to open the valve 92. In such case the water would be expelled from the pumping chamber and the full weight of the float 44 would rest first upon the end 43 of the lever 34, and thereafter would encounter the ring 104 on the lower end of rod 101, adding the weight of the float to :the weight :of w the :arm .98, and thereby openingthe valve: 92.

While air is admittedpast-the valve 111 through the clearance between the valveand .itsguide 115, the discharge check valve 49 in the valvebox Gisopenypermitting water to flow out by way of the discharge pipe 5 to the closed or pressuredelivery system.

During this timethe control check valve 63 isseated as shown in Fig. 1 toprevent air under pressure passing down through the tube-67 andinto-the-discharge valve-box '6.

opening is :presented. The pressure of the air quickly drops below the pressure of the water r'etained in the valvebox G and in-the discharge system with the result that :water pressureinthebox 6 exceeds the'pressure of air in thegpumping chamber 3,-with the result that water is expelled past the check valve .63 through the tube 67=intothe central chamber between the admission'and exhaust valves 1-11.and 106 respectively.

This flow of water preferably continues during the filling stroke in order to insure sufi'icienttransferof heat tothe metal walls which are filled by the 'rapid expansion of air at the: exhaust :valve 106. Obviously, if

desired,"therateat which water is driven out of valve :box 6, that :is, :from ithe discharge system which is winder pressure beyond the check valve 50,:maybe controlled byth-e substitution ofan-orificenipple 61 of the :right size in the elbow 60.

Attention is calledtothe fact that the guide of the dischargeicheck valve stem 52in the -hubi57 is :peculiarly subject to interference with-any-sandor deposit which may be carried in with the water. :By drawing the waterforiheatingthe exhaust .valveand chamber-from the clearance space about the-stem 52 provides the normal function of washing out this clearance space, thereby-to expel any foreignmatter which :mightlbecome lodged in the same.

if desired-the check valvei63 :may travel from its lower seat wherezit prevents the ingress of air intortheivalverboxfi to an opposed seat at :the end oftheztube 67 :where it-would limit :further flow outwardly of water. :In otherwords,:the amount of waterrthen would be controlled by the time that it took the wateritoraisethe check valverfrom its lower .seat to its :upper seattand only a very short squirt :of water wouldibe delivered into the passageway 70.

from its seat.

Obviously water maybe taken :from anywhere-in the dischargesystem above the check valve.50 or in .t'actmight beatakenirom any otherpartofzthe pump orsystem for washing orsprayingsthe exhaustvalvezand its'cadjzacent part with aliquid to prevent ifrosting .orfreezing. It. istozbe observedathatsthe expansion of the air at the admission valve onadmission oflive air tothezpumping chamher tends 1 also -;to cool :the metal of :the :head

-.1 becausethere is acertain wire drawing be- .tween :the admission valve 111 .andits guide 115, such wire drawingibeing usefultoassist in propelling theadmission valvezto itsiseat when the exhaust valve 106 is tforcedaway ,Itwill be seen,:therefore; that evenrthough the pump issubjected to continuous operation .at heavy duty,-the vcontinued expansionof :air in entering and leaving the pumping chamber will be :prevented from frostingior freezing thevalves andpadj acentpartsbecause of-Lthe continued feediugcof :the same by .dis-

charging water upon or into the :vicinity :of

the same. :Itiwillbe-apparentgthat the. latter 1 part of the ,exhauststroke whereair at Ja -pressure :less than the pressure prevailing in the valve box 6. flows out through thepassageway 70 and past theexhaust'valve thi-s will carry with itzthe water which isdischargediby the .pipe 67 and thus keep ;the imetal :parts warm enough to prevent the deposit of frost or ice. 'Imbelieve'it is broadly new to make provision'for passing water out the discharge pipe of a :pneumaticpumpfor defrosting the same.

11 d01not intend :tobe-limited to the details shownand vdescribed.

I claim: 1 '1. :In a pneumatic displacement pum the air discharge passage of said pump which comprises passing water-throughsaid air discharge passage.

2. ,The method of preventing frosting of :the exhaust valve of a pneumatic pump which comprisesspraying the exhaust valve with a small quantity-of the liquid {t0 :be

- pumped for each operation aof the valve.

3. The method of preventing frosting-of 13116 13251121.1181 valve of a pneumatic pump which consists {in carrying a small :amount of water out-.throughathe valve with the ex hausted 1 air.

:4. The method of preventing jfreezinguvof the exhaust valve :of a :pneumatic pump which consists .inspraying the .inside of :the valve with cold water.

5. .The method of preventing ifrostingi'of i the exhaust valve :of a pneumatic ipump which comprises driving water from :the

pumping chamber .by :pneumatic pressure? to place it under-a yieldingpressureihea'daopening :the exhaustvalve to release :the pneu- P 10; having an :air discharge. passage the method :of preventing .the. deposit of frost :adj acent matic pressure, closing oif communication between the discharged water and the compressed air, permitting the escapeof a small quantity of water under pressure and projecting the same'upon the exhaust valve when the pressure .of the water on the discharge side exceeds pressure of the escaping air.

6. In a pneumatic pump having a pumping chamber and a pneumatic exhaust valve, a discharge conduit, a discharge check valve therefor, means for opening the exhaust valve after a charge of liquid has been expelled from the pumping chamber and a discharge connection for discharging liquid from the discharge conduit through the exhaust valve to prevent frosting of the same.

7. In a pneumatic pump having a discharge pipe, a discharge check valve for said pipe, an air exhaust valve, the combination of a tube leading from said discharge pipe above the check valve and directed to discharge the fluid therein into heat exchange relation with said exhaust valve.

8. In a pneumatic pump having a discharge pipe, a discharge check valve for said pipe, and an air exhaust valve, the combination of a tube leading from the discharge pipe above the check valve and directed towards said exhaust valve, and a check valve preventing the flow of air into said discharge p In a pneumatic pump, the combination of a discharge pipe, a discharge check valve box having a check valve for said pipe, a pneumatic exhaust valve, a tube extending from said valve box and directed towards the exhaust valve, and a check valve controlling said tube.

10. In a pneumatic pump, the combination of a discharge pipe, a discharge check valve box having a check valve for said pipe, a pneumatic exhaust valve, a tube extending from said valve box and directed towards the exhaust valve, and a check valve controlling said tube, said check valve comprising a valve housing having a valve seat and a ball valve therein adapted toopen when pressure in the discharge pipe exceeds the pneumatic pressure in the pumping chamber.

11. In a pneumatic pump, the combination of a pumping chamber, air control. valve means for said chamber and including an air exhaust valve, a discharge pipe, a liquid discharge valve box at the lower end of said pipe having a discharge check valve, means including a float guided on the pipe for controlling the opening of the exhaust valve upon predetermined low level of liquid in the chamber, a tube extending from said box towards the exhaust valve and adapted-to discharge liquid towards; the exhaust valve when the exhaust valve is opened.

12. In a pneumatic pump having a pumping chamber and an air exhaust valve, the

combination of means for opening the valve upon low level of liquid in'the pumping chamber, and means for injecting a small quantity'of water into the air escaping past the exhaust valve for each operation of said exhaust valve.

13. In a pneumatic pump, the combination of a pumping chamber, an air exhaust valve for the pumping chamber, means for opening said exhaust valve when liquid has been expelled from the pumping chamber, and means Within the pumping chamber, for spraying water upon the exhaust valve to prevent frosting of the same.

14. In a pneumatic pump, the combination of a pumping chamber, an air exhaust valve for the pumping chamber, means for opening said exhaust valve when liquid has been expelled from the pumping chamber, a liquid discharge check valve having a stem, a guide for the stem providing an annular clearance space, means providing a discharge passageway leading from said clearance space to the exhaust valve for cleaning this space and for discharging liquid onto the exhaust valve to prevent frosting of the same.

15. In a pneumatic pump having a pumping chamber, a discharge pipe, a discharge check valve having a stem, a guide for the stem providing an annular clearance space, and a tube leading from the end of said guide to convey particles out of said clearance space.

V 16. In a pneumatic pump having a pump-1 ing chamber, a discharge pipe, a discharge check valve having a stem, a guide for the stem providing an annular clearance space, a tube leadlng from the end of sa1d gulde to convey particles out of said clearance space,

and a valve for limiting the flow of liquid through said tube in one direction.

17 The method of preventing the deposit of frost near the air valves of a pneumatic displacement pump having passages adjacent said valves which comprises passing water through the passages so as to subject said valves to the latent heat of the water- 18. The method of preventing the deposit of frost in a gas expansion pump having gas discharge passages, which method comprises passing some of the pumped fluid in thermal contact with the gas passages. I

19. In a gas expansion instrumentality for pumping liquids and having a valve and valve passage, the method of preventing the deposit of frost near the valve which Comprlses bringingv some of the liquid into contact with'the passage adjacent said valve.

-20. In a structure employing a gas discharge valve and a passage adjacent, the method of effecting a change of temperature of the valve. whichlcomprises directing a mass of liquid intothe interior ofsaid passage in thermal relation with the valve. 7

21. In a structure employing a gas dis charge valve and a passage adjacent the method of preventing the formation of frost near the valve due to expansion of the gas which comprises directing a flow of fluid in the interior of said passage in thermal relation wIth the valve.

22. In a structure employing a gas discharge valve and a passage adjacent, the method of preventing the formation of frost near the valve due to expansion of the gas which comprises directing a flow of liquid in the interior of said passage in thermal relatlon with the valve whereby the valve and passage are subjected to the latent heat of fusion of the liquid.

In witness whereof I hereunto subscribe my name this 19th day of July, 1928.

BUR-TON S. AIKMAN. 

